I have a 12 Volt 5 AMP battery which I like to use to power motors that are 7.2 volts.I was thinking of building my own voltage regulator using http://www.sparkfun.com/products/527 from Sparkfun. Not sure how to build it so I will have to learn.

Any suggestions on something I can buy that is aready done?I have been looking but not much success.Thanks

Probably not necessary. If you are using a PWM-capable motor driver then you can just drive it with 12V and use PWM (analogWrite()) to set a duty cycle that delivers an effective voltage of 7.2V (or even lower). For example:

Lots of voltage regulators of different types are avalible. First you have to define the maximum current capacity you want the regulator to be able to supply. At higher current levels one really is encouraged to look at switching regulators as the higher efficiencies they have over linear regulators will save a lot of heat problems in your projects.

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I have a 12 Volt 5 AMP battery

I assume you mean a 5 amp/hour rating? A 5 amp/hour battery can supply a lot more then just 5 amps, just for shorter duration.

Interesting...I have a motor shield and just contol the voltage using the output. As long as I don't exceed the max value for 7.2.Yes you are correct 5 amp/hour rating. Lead acid battery which is cheap and use it for testing.I will add a 3 amp fuse to begin and go from there.